The invention relates generally to the field of welding systems and more particularly to sheathed welding wires that improve welding performance.
Welding systems generally make use of electrodes configured to pass an arc between a torch and a work piece, thereby heating the work piece to create a weld, and in certain welding systems melting the electrode to add metal to the weld. A number of forms of welding are known and are generally used in the art. In many systems, such as metal inert gas (MIG) systems, the wire electrode is advanced through a welding torch and is generally consumed by the heat of the arc. In such operations, the wire electrode may also be known as a “filler material” that becomes part of the weld. The electrode may be provided in a variety of materials and forms, including solid wire electrodes and metal-core wire electrodes. Metal-core wire electrodes generally include tubular shaped metal sheath about their exterior and a metal powder core including various powdered materials.
The selection of the type of electrode for a particular welding operation may be based on several factors, including, the composition of the metals being welded, the joint design and the material surface conditions. In general, it is desirable that the weld electrode have mechanical properties similar to those of the base material and no discontinuities, such as porosity. Thus, desirable electrodes may include solid wire electrodes or metal-core wire electrodes that comprise similar compositions to a work piece when they are melted into the weld location. In other words, in a metal-core wire, the core of the wire and the sheath material surrounding the core may combine to define an overall composition when the wire is melted.
Further, the electrode may include properties that affect the quality of the weld. For example, an electrode may dictate the width of the arc, the heat of the weld, the depth of the weld, and the like. The electrode may also affect the ease of welding. For example, a given electrode may be susceptible to sticking of electrode to the work piece during welding and, thus, increase the difficulty of welding.
In addition, depending upon the particular metallurgy of the welding wire, aspects of the welding operation may be less than optimal. For example, certain applications may require specific wire metallurgy. One example is in the manufacture of vehicle exhaust systems, in which solid series 300 stainless steel welding wire is commonly used. However, due to energy density issues, diameter and wetting/viscosity, incidences of burn through can be high. Also, 300 series wire has a tendency to micro-arc or stick during current transfer from the welding torch contact tip to the wire. Such micro-arcing causes contact tip wear and failure, as well as burn back. Moreover, the wire may freeze momentarily, creating process stability problems.
Accordingly, there is need for a welding wire that is compatible with welding applications and that comprises properties that provide for a quality weld.